From: Jean-François Moine <moinejf@free.fr>
Date: Tue, 6 Jul 2010 07:16:40 +0000 (-0300)
Subject: V4L/DVB: gspca - main: Possible race condition in queue management
X-Git-Tag: v2.6.36-rc1~582^2~68
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=02bbcb9d863df10b5a4b91ba5b4c76eaf1340883;p=pandora-kernel.git

V4L/DVB: gspca - main: Possible race condition in queue management

The problem may occur with SMP:
- a frame is completed at interrupt level (in gspca_frame_add with
  packet_type == LAST_PACKET,
- just after clearing the bit V4L2_BUF_FLAG_QUEUED and before setting
  the bit V4L2_BUF_FLAG_DONE, on the other processor, the application
  tries to requeue the same frame buffer,
- then, the qbuf function succeeds because ALL_FLAGS are not set.
The fix sets and resets the two flags in one instruction.

Reported-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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